Update ruby19.spec

- Update for Ruby 1.9.3-p362 release.
- Removed unnecessary '--includedir' and '--libdir', they're both included in the %configure macro
- Added '--with-sitedir' and '--with-vendordir' to match more closely to the RHEL/CentOS RPMs.
- Added 'Provides:' statement for 'rubygem-rake', 'rubygem-json', and 'rubygem-minitest'